This application is related to Japanese Patent Application No. 2000-237266 filed in Aug. 4, 2000, whose priority is claimed under 35 USC xc2xa7119, the disclosure of which is incorporated by reference in its entirety.
1. Field of the Invention
The present invention relates to a disc-like information recording medium represented by an optical disc, optical magnetic disc or phase change optical disc, a disc master and a stamper for manufacturing the disc-like information recording medium, a stamper configuring apparatus for configuring the stamper, and a hub mounting apparatus for mounting a hub to the disc-like information recording medium.
2. Description of the Related Art
There has widely been known a method for fitting a hub into a central hole and adhering the hub by an ultraviolet curing resin in order to increase a disk rotational speed of the disc-like information recording medium such as an optical disc, optical magnetic recording medium, phase change medium or the like made by laminating a transparent dielectric film, magnetic film, reflective film, or the like on a disc substrate.
A manufacturing method of the disc-like information recording medium will be explained hereinbelow with reference to FIGS. 22 to 26 taking an example of a manufacturing method of a conventional optical magnetic recording medium.
FIG. 22 is a typical perspective view of a conventional optical magnetic recording medium. The conventional disc-like information recording medium has a stamper holding channel 103 and an information recording area 102 formed by a guide track or pit line on a disc substrate 101. The disc substrate 101 is made of a resin such as polycarbonate or the like molded by an injection molding method. Laser beam is collectively irradiated to the guide track for recording and reproducing information.
FIG. 23 is a typical perspective view of a disc master for manufacturing the conventional optical magnetic recording medium. A silica glass disc or soda-lime glass is used as a substrate 101 of the disc master. A photosensitive resist is applied to the substrate. Thereafter, a desired guide track or pit line is exposed and developed to form the information recording area 102, thereby obtaining the conventional optical magnetic recording medium. After forming a metal film such as Ni, Ta or the like on the disc master as an electrode film, an electroforming process is executed by using a doping of Ni metal plating, to thereby obtain an Ni stamper.
The Ni stamper is generally formed to have a thickness of 0.2 mm to 0.5 mm. The guide track or pit line formed on the disc master is transferred to the Ni stamper.
The inside and outside diameters of the stamper are stamped out so as to match with the shape of the injection molding apparatus that is for molding the Ni stamper into the disc substrate 101, and then, it is mounted to the injection molding apparatus. Resin such as polycarbonate or the like is melted to be flown into the molding for forming the disc substrate 101.
Formed on the disc substrate 101 by a sputtering apparatus are dielectric film, metal magnetic film and reflective film. Thereafter, a back coat resin is applied thereon for coating the film to thereby obtain optical magnetic recording medium.
As shown in FIG. 24, a hub 108 mounted to the optical magnetic recording medium and having a collar portion is usually used. A ultraviolet curing resin or thermal curing resin is applied to the position where the collar portion is in contact with the disc substrate 101 for adhering the hub 108 to the disc substrate 101.
There has conventionally been used a method for detecting the position of the guide track or pit line with an optical technique to perform a position alignment with the hub 108 in order to reduce the eccentricity of the disc-like information recording medium by coinciding the rotational center of the disc substrate 101 to which the hub 108 has already been installed with the rotational center of the information recording area 102 formed on the disc substrate 101 and provided with the guide track or pit line.
FIGS. 25 and 26 respectively show a schematic view of a conventional hub mounting apparatus. As shown in FIGS. 25 and 26, the conventional hub mounting apparatus has a disc supporting table 105 and hub fixing member 106 wherein the hub 108 is supported by the hub fixing member 106.
In case where the hub 108 is mounted by using the ultraviolet curing resin, the ultraviolet curing resin is applied in advance to the portion on the disc substrate where the hub is installed (opposite to the collar portion).
The optical center position alignment is performed on the disc supporting table 105 to the disc substrate 101 to which the ultraviolet curing resin is applied for coinciding the rotational center of the guide track or pit line with the center of the hub 108. Thereafter, the hub fixing member 106 moves downward for installing the hub 108 to the disc substrate 101. Ultraviolet ray is irradiated to the disc substrate 101 to which the hub 108 is installed for fixing the hub 108 to the disc substrate 101.
However, the conventional position alignment method requires an optical position alignment with respect to the individual medium, resulting in entailing a problem of taking more time for mounting the hub with high precision and being costly to make an apparatus for performing the position alignment. In order to solve the above problems, Japanese Unexamined Patent Publication No. SHO 64(1989)-14747 discloses a method for performing the position alignment of the disc substrate 101 and the hub 108 with a stamper holding plate for installing the stamper to the injection molding apparatus, with a channel 103 (see, FIG. 22) formed on the disc substrate being as a guide. However, this method causes a shift of the mounting position due to a tolerance between the inside diameter of the stamper and the outside diameter of the stamper holder, thereby entailing a drawback of shifting the rotational center of the information recording area 102 from the rotational center of the hub 108. Therefore, this method has a problem of increasing the eccentricity in case where the precision upon stamping out the stamper is low.
The present invention is established to solve the above-mentioned problems, and aims to provide a disc-like information recording medium having extremely small eccentricity with a hub by precisely performing a position alignment of a disc substrate and a hub with a simple method.
The present invention provides a disc-like recording medium provided with a disc substrate having a hole at its center and a circular information recording area at its surface that is concentric with the hole, and a hub that is fitted to the hole, wherein the disc substrate has a relief portion thereon for position alignment of the hub. Further, the invention provides a stamper, a stamper configuring apparatus, a disc master and a hub mounting apparatus.